Drying kilns are employed to dry and season a variety of products, particularly lumber. In the lumber industry drying kilns are employed to season green wood and partially air dried wood. Typically, an elongated structure is employed, currently between 60' and 110' long, in which one or more stacks of green lumber are arranged so that a flow of drying air may be directed over and through those stacks and thereby dry the lumber. Typically, fans are employed either to draw air via conventionally arranged ducting through the stack from one end thereof, or to force air through the stack through one side and out the other side and then recirculate the drying air back to the stack through further conventionally arranged ducting. State of the art systems employ both temperature and humidity controls associated with fan means and ducting to control the humidity and temperature of the drying air and to force it through or pull it through the stacks of green lumber until such time as the lumber has reached the desired degree of dryness.
The problem of directing the flow of drying air efficiently through and over the stack of green lumber has long begged a solution. Woolhouse (U.S. Pat. No. 1,919,646) discloses a curtain means 16 employed in such an attempt. One device disclosed in U.S. Pat. No. 3,196,554 to Smith discloses a series of supposedly inflatible baffles to serve much the same purpose as a series of Woolhouse's curtains for nonheated predrying. No known methods effectively baffle substantially all of the drying airflow from flowing around the product stack. Current methods of regulating airflow require considerable power consumption by the fan means since substantial amounts of drying airflow escape around the sides of the stacks of lumber and thus require wasted recirculation by the fans.
Current methods of baffling also require either uniform loads within a particular kiln or at least loads which do not vary significantly in surface dimension over the length of any particular side of the load. Even the baffles disclosed by Smith permit airflow to escape in a somewhat winding path around the edges of the various interwoven baffles therein disclosed, assuming that a Smith baffle could be made to inflate and effectively seal against the load surface at all.
It is essential that this drying operation be cost effective particularly in times when the lumber industry is troubled, and thus it is necessary to employ a standard sized kiln which can accomodate various sizes of stacked green loads of lumber.